Non-contact power reception device and vehicle including the same

ABSTRACT

A non-contact power reception device includes a load such as a power storage device identified as a subject of power feeding, and a secondary self-resonant coil receiving electric power to be supplied to said load from an external primary self-resonant coil. The secondary self-resonant coil is configured so as to be switchable between a first state and a second state. The first state is selected in a power reception mode in which the secondary self-resonant coil is magnetically coupled with the primary self-resonant coil through resonance of a magnetic field. The second state is selected in a power non-reception mode in which the magnetic coupling of the secondary self-resonant coil with the primary self-resonant coil through resonance is weaker than in the first state.

TECHNICAL FIELD

The present invention relates to a non-contact power reception deviceand a vehicle including the same, particularly, to the technique ofsupplying electric power to a vehicle in a non-contact manner from apower source external to the vehicle.

BACKGROUND ART

Great attention is focused on electrical powered vehicles such as anelectric vehicle and hybrid vehicle as environment-friendly vehicles.These vehicles incorporate an electric motor for generating a drivingforce for running, and a rechargeable power storage device for storingelectric power to be supplied to the electric motor. A hybrid vehiclerefers to a vehicle incorporating an internal combustion engine as apower source, in addition to an electric motor, or a vehicle furtherincorporating a fuel cell in addition to a power storage device as thedirect current power source for driving the vehicle.

Among the hybrid vehicles there is known a vehicle that allows chargingof the vehicle-mounted power storage device from a power source externalto the vehicle, likewise with an electric vehicle. For example, theso-called “plug-in hybrid vehicle” is known that allows the powerstorage device to be charged from a general household power supply byestablishing connection between the plug socket located at anestablishment and the charging inlet provided at the vehicle through acharging cable.

As a method for power transfer, attention is recently focused onwireless electrical power transmission without using power supply cordsand/or cables for electrical transmission. Three promising approaches ofthis wireless power transfer technique are known, i.e. power transferusing electromagnetic induction, power transfer using electromagneticwaves, and power transfer through the resonance method.

The resonance method thereof is a non-contact power transfer approachtransferring power via an electromagnetic field by causing resonance ata pair of resonators (for example, a pair of self-resonant coils) at theelectromagnetic field (near field), allowing electric power as high asseveral kW to be transferred over a relatively long distance (forexample, several meters) (refer to Non-Patent Document 1).

Patent Document 1: WO 2007/008646

Non-Patent Document 1: Andre Kurs et al., “Wireless Power Transfer viaStrongly Coupled Magnetic Resonances”, [online], Jul. 6, 2007, SCIENCE,Volume 317, pp. 83-86, [Searched on Sep. 12, 2007], Internet <URL;http://www.sciencemag. org/cgi/reprint/317/5834/83.pdf>

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In the resonance method, electric power is transferred when thecondition for resonance between a resonator of the power transmissionside and a resonator of the power reception side is met. However, thereis a case where the power reception side does not desire reception ofelectric power such as when the power storage device is at a full stateor the like.

In the case where the wireless power transfer technique disclosed in theaforementioned “Wireless Power Transfer via Strongly Coupled MagneticResonances” is applied to a power feeding system for a vehicle, how thepower reception is to be stopped when power reception at the vehicle isnot required is an issue. The aforementioned documents do notparticularly teach about a specific configuration or control approachfor stopping power reception.

An object of the present invention is to provide a non-contact powerreception device and vehicle that can stop power reception reliably inpower feeding using a resonance method.

Means for Solving the Problems

A non-contact power reception device according to the present inventionincludes a load identified as a subject of power feeding, and asecondary self-resonant coil receiving electric power to be supplied tothe load from a primary self-resonant coil external to the vehicle. Thesecondary self-resonant coil is configured so as to be switchablebetween a first state and a second state. The first state is selected ina power reception mode in which the secondary self-resonant coil ismagnetically coupled with the primary self-resonant coil throughresonance of a magnetic field. The second state is selected in a powernon-reception mode in which the magnetic coupling of the secondaryself-resonant coil with the primary self-resonant coil through resonanceis weaker than in the first state.

Preferably, the secondary self-resonant coil has an impedance differingbetween the first state and the second state.

More preferably, the secondary self-resonant coil includes a coil bodyand an inductance modifier modifying the inductance of the coil body.

Further preferably, the coil body is divided at a central region into afirst portion and a second portion. The inductance modifier includes arelay provided at the central region of the coil body, connecting thefirst portion and the second portion in a power reception mode, anddisconnecting the first portion from the second portion in a powernon-reception mode.

Preferably, the secondary self-resonant coil includes a coil body, and acapacitance modifier modifying the capacitance of the coil body.

Further preferably, the capacitance modifier includes a leading lineconnected to an end of the coil body, a relay connected to the leadingline, and a capacitor connected to the coil body via the leading line bythe relay in a power reception mode, and disconnected from the coil bodyby the relay in a power non-reception mode.

Further preferably, the non-contact power reception device furtherincludes a discharging resistor for setting the capacitor at adischarging state in a power non-reception mode.

Further preferably, there is included another relay disconnecting thedischarging resistor from the capacitor in a power reception mode, andconnecting the discharging resistor with the capacitor in a powernon-reception mode.

Further preferably, the relay disconnects the discharging resistor fromthe capacitor in a power reception mode, and connects the dischargingresistor with the capacitor in a power non-reception mode.

Preferably, the non-contact power reception device further includes avoltage converter voltage-converting an input voltage for supply to aload, and a rectifier rectifying AC voltage and providing the rectifiedvoltage to the voltage converter as the input voltage. The secondaryself-resonant coil receives electric power from the primaryself-resonant coil to cause generation of AC voltage to be supplied tothe rectifier.

Further preferably, the non-contact power reception device is mounted ona vehicle to receive electric power from a feeding device including theprimary self-resonant coil external to the vehicle. The non-contactpower reception device further includes a control unit controllingswitching of the secondary self-resonant coil between the first stateand the second state. The control unit sets the secondary self-resonantcoil at the first state and the second state when the vehicle meets andnot meets, respectively, a power reception condition.

Further preferably, the vehicle includes a power storage devicereceiving charge electric power from the non-contact power receptiondevice as the load. The power reception condition includes the conditionthat the state of charge of the power storage device is less than athreshold value.

More preferably, the power reception condition includes the conditionthat a predetermined failure is not occurring at the vehicle.

According to another aspect of the present invention, a vehicle includesa non-contact power reception device receiving electric powertransferred in a non-contact manner from outside the vehicle. Thenon-contact power reception device includes a load identified as thesubject of power feeding, and a secondary self-resonant coil receivingelectric power to be supplied to the load from an external primaryself-resonant coil. The secondary self-resonant coil is configured so asto be switchable between a first state and a second state. The firststate is selected in a power reception mode in which the secondaryself-resonant coil is magnetically coupled with the primaryself-resonant coil through resonance of a magnetic field. The secondstate is selected in a power non-reception mode in which the magneticcoupling of the secondary self-resonant coil with the primaryself-resonant coil through resonance is weaker than in the first state.

Preferably, the secondary self-resonant coil has an impedance differingbetween the first state and the second state.

Effects of the Invention

According to the present invention, power reception can be stoppedreliably when reception of electric power is not desired in powerfeeding using a resonance method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents an entire configuration of a power feeding systemaccording to a first embodiment of the present invention.

FIG. 2 is a diagram to describe the mechanism of power transmission by aresonance method.

FIG. 3 represents the relationship between the distance from a currentsource (magnetic current source) and intensity of the electromagneticfield.

FIG. 4 is a block diagram representing a powertrain configuration of anelectrical powered vehicle 100 shown in FIG. 1.

FIG. 5 is a circuit diagram of a DC/DC converter 140 shown in FIG. 1.

FIG. 6 represents a detailed configuration of a secondary self-resonantcoil 110 of FIGS. 1 and 4.

FIG. 7 is a flowchart to describe a charge start process executed by avehicle ECU 180.

FIG. 8 is a flowchart of a process in the case of normal terminationduring power reception.

FIG. 9 is a flowchart of a process in the case of forced termination dueto occurrence of an error during power reception.

FIG. 10 is a circuit diagram of a configuration of a secondaryself-resonant coil 110A employed in a non-contact power reception deviceof a second embodiment.

FIG. 11 is a circuit diagram of a configuration of a secondaryself-resonant coil 110A1 that is a modification of secondaryself-resonant coil 110A.

FIG. 12 is a circuit diagram of a configuration of a secondaryself-resonant coil 110B that is a modification of secondaryself-resonant coil 110A.

FIG. 13 is a circuit diagram of a configuration of a secondaryself-resonant coil 110C that is another modification of secondaryself-resonant coil 110A.

DESCRIPTION OF THE REFERENCE SIGNS

100 electrical powered vehicle; 110, 110A, 110A1, 110B, 110C, 340secondary self-resonant coil; 111 coil body; 112 relay; 113 firstportion; 114 second portion; 115 inductance modifier; 125, 350 secondarycoil; 130 rectifier; 140 converter; 142 DC/AC conversion unit; 144transformer unit; 146 rectifier unit; 150 power storage device; 162boost converter; 164, 166 inverter; 170 motor; 172, 174 motor generator;176 engine; 177 power split device; 178 driving wheel; 190 communicationdevice; 191, 192 voltage sensor; 194 current sensor; 200 power feedingdevice; 210 AC power source; 220 high frequency power driver; 230, 320primary coil; 240, 330 primary self-resonant coil; 250 communicationdevice; 310 high frequency power source; 311 coil body; 312A, 312A1,312B, 312C capacitance modifier; 313 capacitor; 314 dischargingresistor; 315, 316, 317 relay; 321, 322 leading line; 360 load; 180vehicle ECU; PL2 positive line; SMR1, SMR2 system main relay.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described hereinafter indetail with reference to the drawings. The same or correspondingelements in the drawings have the same reference characters allotted,and description thereof will not be repeated.

First Embodiment

FIG. 1 represents an entire configuration of a power feeding systemaccording to a first embodiment of the present invention. Referring toFIG. 1, the power feeding system includes an electrical powered vehicle100, and a power feeding device 200. Electrical powered vehicle 100includes a secondary self-resonant coil 110, a secondary coil 120, arectifier 130, a DC/DC converter 140, and a power storage device 150.Electrical powered vehicle 100 further includes a power control unit(hereinafter, also referred to as PCU) 160, a motor 170, a vehicle ECU(Electronic Control Unit) 180, and a communication device 190.

Although secondary self-resonant coil 110 is arranged at the lowerportion of the vehicle body, it may be arranged at the upper portion ofthe vehicle body if power feeding device 200 is disposed above thevehicle. Secondary self-resonant coil 110 is an LC resonant coil havingboth ends open (non-connected), and receives the electric power frompower feeding device 200 by resonating with a primary self-resonant coil240 of power feeding device 200 (described afterwards) via anelectromagnetic field. Although the capacitor component of secondaryself-resonant coil 110 corresponds to the floating capacitance of thecoil here, a capacitor may be provided across the ends of the coil.

Secondary self-resonant coil 110 has its number of windings setappropriately such that the Q value representing the resonance strengthbetween primary self-resonant coil 240 and secondary self-resonant coil110 (for example, Q>100), the κ value representing the degree ofcoupling thereof and the like become higher based on the distance fromprimary self-resonant coil 240 of power feeding device 200, the resonantfrequency of primary self-resonant coil 240 and secondary self-resonantcoil 110, and the like.

Secondary coil 120 is arranged coaxial with secondary self-resonant coil110, and can be coupled magnetically with secondary self-resonant coil110 by electromagnetic induction. Secondary coil 120 extracts theelectric power received by secondary self-resonant coil 110 throughelectromagnetic induction for output to rectifier 130. Rectifier 130rectifies AC power extracted by secondary coil 120.

DC/DC converter 140 responds to a control signal from vehicle ECU 180 toconvert the electric power rectified by rectifier 130 to the voltagelevel of power storage device 150 for output thereto. In the ease wherepower is received from power feeding device 200 during a runningoperation of the vehicle (in this case, power feeding device 200 may bearranged, for example, at the upper portion or side portion of thevehicle), DC/DC converter 140 may convert the electric power rectifiedby rectifier 130 into system voltage for direct supply to PCU 160. DC/DCconverter 140 is not necessarily required, and a configuration may beemployed in which the AC electric power extracted by secondary coil 120is rectified by rectifier 130 and then directly applied to power storagedevice 150.

Power storage device 150 is a rechargeable DC power source, and includesa secondary battery such as of lithium ion or nickel-metal hydride.Power storage device 150 stores the electric power supplied from DC/DCconverter 140, as well as the regenerative electric power generated bymotor 170. Power storage device 150 supplies the stored electric powerto PCU 160. A capacitor of large capacitance may be employed as powerstorage device 150. Any power buffer is applicable as long as it cantemporarily store the electric power supplied from power feeding device200 and/or the regenerative electric power from motor 170 and supply thestored electric power to PCU 160.

PCU 160 drives motor 170 by the electric power output from power storagedevice 150 or the electric power directly supplied from DC/DC converter140. PCU 160 rectifies the regenerative electric power generated bymotor 170 for output to power storage device 150, whereby power storagedevice 150 is charged. Motor 170 is driven by PCU 160 to generatevehicle driving power, which is provided to driving wheels. Motor 170generates electric power using the kinetic energy received from drivingwheels and an engine not shown, and outputs the generated regenerativeelectric power to PCU 160.

In a vehicle running mode, vehicle ECU 180 controls PCU 160 based on thevehicle running state and/or the state of charge (hereinafter, alsoreferred to, as “SOC”) of power storage device 150. Communication device190 functions as a communication interface for wireless communicationwith power feeding device 200 external to the vehicle.

Power feeding device 200 includes an AC power source 210, a highfrequency power driver 220, a primary coil 230, a primary self-resonantcoil 240, a communication device 250, and an ECU 260.

AC power source 210 is external to the vehicle, and is a system powersource, for example. High frequency power driver 220 converts theelectric power received from AC power source 210 into an electric powerof high frequency. The converted high frequency electric power issupplied to primary coil 230. The frequency of the high frequencyelectric power generated by high frequency power driver 220 is 1 M toten and several MHz, for example.

Primary coil 230 is arranged coaxial with primary self-resonant coil240, and can be coupled magnetically with primary self-resonant coil 240by electromagnetic induction. Primary coil 230 feeds the high frequencyelectric power supplied from high frequency power driver 220 to primaryself-resonant coil 240 by electromagnetic induction.

Although primary self-resonant coil 240 is arranged in proximity to theground, it may be arranged above or at the side of the vehicle in thecase where power is fed to electrical powered vehicle 100 from above thevehicle. Primary self-resonant coil 240 is similarly an LC resonant coilhaving both ends open (non-contact), and transfers electric power toelectrical powered vehicle 100 by resonating with secondaryself-resonant coil 110 of electrical powered vehicle 100 via anelectromagnetic field. Although the capacitor component of primaryself-resonant coil 240 similarly corresponds to the floating capacitanceof the coil, a capacitor may be connected across the ends of the coil.

Primary self-resonant coil 240 has its number of windings setappropriately such that the Q value (for example, Q>100), the couplingdegree κ and the like become higher based on the distance from secondaryself-resonant coil 110 of electrical powered vehicle 100, the resonantfrequency of primary self-resonant coil 240 and secondary self-resonantcoil 110, and the like.

Communication device 250 functions as a communication interface toeffect wireless communication with electrical powered vehicle 100 thatis the destination of power feeding. ECU 260 controls high frequencypower driver 220 such that the reception electric power at electricalpowered vehicle 100 attains a target value. Specifically, ECU 260obtains from electrical powered vehicle 100 the reception electric powerand its target value of electrical powered vehicle 100 throughcommunication device 250 and controls the output of high frequency powerdriver 220 such that the reception electric power at electrical poweredvehicle 100 matches the target value. ECU 260 can transmit the impedancevalue of power feeding device 200 to electrical powered vehicle 100.

FIG. 2 is a diagram to describe the mechanism of power transmission bythe resonance method. Referring to FIG. 2, the resonance method issimilar to the resonance of two tuning forks. By the resonance of two LCresonant coils having the same natural frequency at the electromagneticfield (near field), electric power is transferred from one coil to theother coil via the electromagnetic field.

Specifically, primary coil 320 is connected to high frequency powersource 310, and electric power of a frequency as high as 1 M to ten andseveral MHz is supplied to primary self-resonant coil 330 that ismagnetically coupled with primary coil 320 by electromagnetic induction.Primary self-resonant coil 330 is an LC resonator based on the coil'sinductance and floating capacitance, resonating with secondaryself-resonant coil 340 having the same resonant frequency as primaryself-resonant coil 330 via an electromagnetic field (near field).Accordingly, energy (electric power) is transferred from primaryself-resonant coil 330 to secondary self-resonant coil 340 via theelectromagnetic field. The energy (electric power) transferred tosecondary self-resonant coil 340 is extracted by secondary coil 350magnetically coupled with secondary self-resonant coil 340 throughelectromagnetic induction to be provided to a load 360.

The corresponding relationship with the elements in FIG. 1 will bedescribed hereinafter. AC power source 210 and high frequency powerdriver 220 of FIG. 1 correspond to high frequency power source 310 ofFIG. 2. Primary coil 230 and primary self-resonant coil 240 of FIG. 1correspond to primary coil 320 and primary self-resonant coil 330,respectively, of FIG. 2. Secondary self-resonant coil 110 and secondarycoil 120 of FIG. 1 correspond to secondary self-resonant coil 340 andsecondary coil 350, respectively, of FIG. 2. The elements of rectifier130 and et seq. of FIG. 1 are generically represented as load 360.

FIG. 3 represents the relationship between the distance from a currentsource (magnetic current source) and the electromagnetic fieldintensity. Referring to FIG. 3, the electromagnetic field includes threecomponents. Curve k1 represents a component inversely proportional tothe distance from the wave source, and is referred to as “radiationelectromagnetic field”. Curve k2 represents a component inverselyproportional to the square of the distance from the wave source, and isreferred to as “induction electromagnetic field”. Curve k3 represents acomponent inversely proportional to the cube of the distance from thewave source, and is referred to as “electrostatic electromagneticfield”.

There is a region thereof where the intensity of the electromagneticwave decreases drastically according to the distance from the wavesource. In the resonance method, energy (electric power) is transmittedtaking advantage of the near field (evanescent field). Specifically, bycausing a pair of resonators (for example, pair of LC resonant coils)having the same natural frequency to resonate taking advantage of thenear field, energy (electric power) is transmitted from one resonator(primary self-resonant coil) to the other resonator (secondaryself-resonant coil). Since this near field does not pass on energy(electric power) far away, the resonance method allows powertransmission with lower energy loss as compared to an electromagneticwave that transmits energy (electric power) by the “radiationelectromagnetic field” that passes on energy over a great distance.

FIG. 4 is a block diagram representing a powertrain configuration ofelectrical powered vehicle 100 of FIG. 1, Referring to FIG. 4,electrical powered vehicle 100 includes a power storage device 150, asystem main relay SMR1, a boost converter 162, inverters 164, 166, motorgenerators 172, 174, an engine 176, a power split device 177, and adriving wheel 178. Additionally, electrical powered vehicle 100 furtherincludes secondary self-resonant coil 110, secondary coil 120, rectifier130, DC/DC converter 140, system main relay SMR2, vehicle ECU 180,communication device 190, voltage sensors 191, 192, and current sensor194.

Electrical powered vehicle 100 incorporates engine 176 and motorgenerator 174 as the driving source. Engine 176 and motor generators 172and 174 are coupled with power split device 177. Electrical poweredvehicle 100 runs by the driving power generated by at least one ofengine 176 and motor generator 174. The power generated by engine 176 isdivided into two paths by power split device 177. Specifically, one pathis directed to driving wheel 178, and the other path is directed tomotor generator 172.

Motor generator 172 is an AC rotating electric machine formed of, forexample, a 3-phase AC synchronous electric motor having a permanentmagnet embedded in a rotor. Motor generator 172 generates electric powerusing the kinetic energy of engine 176 divided by power split device177. For example, when the SOC of power storage device 150 becomes lowerthan a predetermined value, engine 176 is started and electric power isgenerated by motor generator 172, whereby power storage device 150 ischarged.

Motor generator 174 is also an AC rotating electric machine formed of,for example, a 3-phase AC synchronous electric motor having a permanentmagnet embedded in a rotor, likewise with motor generator 172. Motorgenerator 174 generates driving power using at least one of the electricpower stored at power storage device 150 and the electric powergenerated by motor generator 172. The driving power of motor generator174 is transmitted to driving wheel 178.

In a braking mode of the vehicle or in an acceleration reducing mode ata downward slope, the mechanical energy stored at the vehicle as akinetic energy or potential energy is used for the rotational drive ofmotor generator 174 through driving wheel 178, whereby motor generator174 operates as a power generator. Accordingly, motor generator 174operates as a regenerative brake converting the running energy intoelectric power to generate the braking force. The electric powergenerated by motor generator 174 is stored in power storage device 150.Motor generator 174 corresponds to motor 170 shown in FIG. 1.

Power split device 177 is formed of a planetary gear set including a sungear, a pinion gear, a carrier, and a ring gear. The pinion gear engageswith the sun gear and ring gear. The carrier supports the pinion gear toallow rotation on its axis, and is coupled to the crankshaft of engine176. The sun gear is coupled to the rotational shaft of motor generator172. The ring gear is coupled to the rotational shaft of motor generator174 and to driving wheel 178.

System main relay SMR1 is disposed between power storage device 150 andboost converter 162. System main relay SMR1 electrically connects powerstorage device 150 with boost converter 162 when a signal SE1 fromvehicle ECU 180 is rendered active, and disconnects the electrical pathbetween power storage device 150 and boost converter 162 when signal SE1is rendered inactive.

Boost converter 162 responds to a signal PWC from vehicle ECU 180 toboost the voltage output from power storage device 150 for output ontopositive line PL2. This boost converter 162 includes, for example, a DCchopper circuit.

Inverters 164 and 166 are provided corresponding to motor generators 172and 174, respectively. Inverter 164 drives motor generator 172 based ona signal PWI1 from vehicle ECU 180. Inverter 166 drives motor generator174 based on a signal PWI2 from vehicle ECU 180. Each of inverters 164and 166 includes a 3-phase bridge circuit, for example.

Boost converter 162 and inverters 164 and 166 correspond to PCU 160 ofFIG. 1.

Secondary self-resonant coil 110 is divided into two at the centralregion where a relay 112 is provided. In a power reception mode, relay112 is controlled to attain a connected state by a control signal SE3from the vehicle ECU. The impedance of secondary self-resonant coil 110is modified to an impedance (first state) allowing resonance withprimary self-resonant coil 240 of FIG. 1. In a power reception stopmode, relay 112 is controlled to attain a non-connected state by controlsignal SE3 from the vehicle ECU. The impedance of secondaryself-resonant coil 110 is modified to an impedance (second state) notallowing resonance with primary self-resonant coil 240 of FIG. 1.

Secondary coil 120, rectifier 130, and DC/DC converter 140 are asdescribed with reference to FIG. 1. Therefore, description thereof willnot be repeated. System main relay SMR2 is arranged between DC/DCconverter 140 and power storage device 150. System main relay SMR2electrically connects power storage device 150 with DC/DC converter 140when a signal SE2 from vehicle ECU 180 is rendered active, anddisconnects the electrical path between power storage device 150 andDC/DC converter 140 when signal SE2 is rendered inactive.

Voltage sensor 191 detects the inter-line voltage V2 of the powertransmission paths between system main relay SMR2 and DC/DC converter140, and provides the detection value to vehicle ECU 180. Voltage sensor192 detects the inter-line voltage VH of the power transmission pathsbetween rectifier 130 and DC/DC converter 140, and provides thedetection value to vehicle ECU 180. Current sensor 194 detects a currentI1 output from rectifier 130 and provides the detection value to vehicleECU 180.

Vehicle ECU 180 generates signals PWC, PWI1 and PWI2 to drive boostconverter 162, motor generator 172, and motor generator 174,respectively, based on the accelerator pedal position, vehicle speed,and signals from various sensors. The generated signals PWC, PWI1 andPWI2 are output to boost converter 162, inverter 164, and inverter 166,respectively.

In a vehicle running mode, vehicle ECU 180 renders signal SE1 active toturn on system main relay SMR1, and renders signal SE2 inactive to turnoff system main relay SMR2. In the case where electric power can bereceived from the power feeding device during a running mode of thevehicle, vehicle ECU 180 may render signals SE1 and SE2 active to turnon both system main relays SMR1 and SMR2.

In a power receiving mode from power feeding device 200 external to thevehicle, vehicle ECU 180 renders signal SE1 inactive to turn off systemmain relay SMR1, and renders signal SE2 active to turn on system mainrelay SMR2.

Vehicle ECU 180 generates a signal PWD to control DC/DC converter 140and provides the generated signal PWD to DC/DC converter 140. Inaddition, vehicle ECU 180 calculates the reception electric power frompower feeding device 200 based on voltage VH from voltage sensor 192 andcurrent I1 from current sensor 194 and transmits the calculated value topower feeding device 200 through communication device 190 together withthe target value of the reception electric power.

FIG. 5 is a circuit diagram of DC/DC converter 140 shown in FIG. 4.Referring to FIG. 5, DC/DC converter 140 includes a DC/AC conversionunit 142, a transformer unit 144, and a rectifier unit 146. DC/ACconversion unit 142 includes a switching element driven on/off based onsignal PWD from vehicle ECU 180 to convert the DC power supplied fromrectifier 130 of FIG. 4 into AC power for output to transformer unit144.

Transformer unit 144 insulates DC/AC conversion unit 142 from rectifierunit 146 and carries out voltage conversion according to the coilwinding ratio. Rectifier unit 146 rectifies the AC power output fromtransformer unit 144 into DC power for output to power storage device150 of FIG. 4.

FIG. 6 represents a detailed configuration of secondary self-resonantcoil 110 of FIGS. 1 and 4.

Referring to FIG. 6, secondary self-resonant coil 110 is configured soas to be switchable between a first state and a second state. The firststate is selected in a power reception mode in which secondaryself-resonant coil 110 is magnetically coupled with primaryself-resonant coil 240 of FIG. 1 through resonance. The second state isselected in a power non-reception mode in which the coupling ofsecondary self-resonant coil 110 with primary self-resonant coil 240 isweaker than in the first state.

Preferably, secondary self-resonant coil 110 has an impedance differingbetween the first state and the second state.

Specifically, secondary self-resonant coil 110 includes a coil body 111,and an impedance modifier 115 modifying the impedance of coil body 111.

Coil body 111 is divided at the central region into a first portion 113and a second portion 114. Impedance modifier 115 includes a relay 112provided at the central region of coil body 111 to connect anddisconnect first portion 113 with/from second portion 114 in a powerreception mode and a power non-reception mode, respectively.

Secondary self-resonant coil 110 operates as an antenna in a powerreception mode. The amplitude of the voltage at the ends is increased,and the amplitude of the voltage at the central region becomessubstantially 0. Therefore, by arranging relay 112 at the central regionof coil body 111, only a small relay having a low breakdown voltage willbe required as compared with the case where the relay is provided atother regions.

In the case where transmission of electric power is effected by way ofthe resonance method, the power transmission side is providing power. Ifthe resonant frequency of the resonant coils matches each other,electric power will be received at the secondary self-resonant coil thatis a component mounted on the vehicle even in the case where powerreception is not intended at the power reception side. Thus, aconfiguration is employed to allow modification of the impedance of thesecondary self-resonant coil, as shown in FIG. 6. In the case where thepower reception side does not intend to receive power, the impedance ismodified so that the resonant frequency does not match that of the powertransmission side.

This is preferable to avoid power reception at a component mounted onthe vehicle not requiring power reception.

FIG. 7 is a flowchart to describe a charge start process executed atvehicle ECU 180. The process shown in this flowchart is invoked from apredetermined main routine to be executed.

Referring to FIG. 7, a determination is made whether there is a chargestart command or not at step S1. A charge start command can be given bya passenger depressing a charge start button or the like. When a chargestart command is given at step S1, control proceeds to step S2. When acharge start command is absent, control is transferred to the mainroutine at step S19.

When control proceeds to step S2, vehicle ECU 180 establishescommunication with power feeding device 200 through communication device190 of FIG. 1. At step S3, a welding check of system main relay SMR2 isexecuted.

Since power storage device 150 is disconnected when system main relaySMR2 attains an OFF state, voltage V2 detected by voltage sensor 191 ofFIG. 4 should be reduced. By controlling system main relay SMR2 toattain an OFF state and confirming that voltage V2 has become lower thana predetermined threshold value that is set lower than the voltage ofpower storage device 150, it is recognized that system main relay SMR2is set OFF properly and not welded. The result of welding check at stepS3 is determined at step S4.

When a determination is made that welding has occurred at SMR2 at stepS4, control proceeds to step S12. The determination result of weldingoccurred at SMR2 is ascertained and stored/notified. At step S14,vehicle ECU 180 requests power feeding device 200 through communicationdevice 190 to stop power transmission. Then, the process ends at stepS15.

When a determination is made that welding is not occurring at SMR2 atstep S4, control proceeds to step S5. At step S5, vehicle ECU 180controls relay 112 provided at secondary self-resonant coil 110 toattain an OFF state. Then, vehicle ECU 180 requests power feeding device200 through communication device 190 to transmit power.

When power is transmitted from power feeding device 200, primaryself-resonant coil 240 is controlled at the resonant frequency. If relay112 is welded, the impedance of secondary self-resonant coil 110 willmatch that of primary self-resonant coil 240 with corresponding resonantfrequency, causing secondary self-resonant coil 110 to resonate withprimary self-resonant coil 240. Accordingly, electric power will betransferred so that voltage VH increases via secondary coil 120 andrectifier 130 of FIG. 4.

Therefore, by checking whether voltage VH is boosted or not at step S7,a determination of relay 112 being welded can be made. When boosting ofvoltage VH is detected at step S7, control proceeds to step S16. At stepS16, the determination result of welding occurred at relay 112 isascertained, and stored/notified. At step S17, vehicle ECU 180 requestspower feeding device 200 through communication device 190 to stop powertransmission. At step S18, the process ends. The electric powertransferred for the purpose of welding check at step S6 is extremelyweak, and smaller than the electric power transferred afterwards at stepS11 for actual power transmission.

In the case where boosting of voltage VH is not detected at step S7,control proceeds to step S8. At step S8, relay 112 is rendered OFFnormally, and a determination is made that welding is not occurring. Atstep S9, vehicle ECU 180 requests power feeding device 200 throughcommunication device 190 to temporarily stop power transmission. At stepS10, vehicle ECU 180 controls relay 112 that is at an OFF state andsystem main relay SMR2 to both attain an ON state. At step S11, vehicleECU 180 requests power feeding device 200 through communication device190 to temporarily stop power transmission. At step S12, a chargingprocess is initiated. Then, control is transferred to the main routineat step S19.

FIG. 8 is a flowchart of a process in the case of normal terminationduring power reception.

Referring to FIG. 8, whether a normal termination trigger is generatedor not is monitored at step S51 during a power reception mode of thenon-contact power reception device of the vehicle. A normal terminationtrigger is generated in the case where charging has progressed such thatthe state of charge (SOC) of power storage device 150 reaches theadministrative upper limit (the value of full charge), in the case wherethe charge end button has been depressed, and in the case where thebattery temperature or battery voltage is outside a predetermined rangesuitable for charging.

Control proceeds to step S58 when such a normal termination trigger isnot generated, and control is transferred to the main routine. In thiscase, the power reception condition is met, and secondary self-resonantcoil 110 is controlled to attain a state capable of receiving power.Then, step S51 is executed again at an elapse of a predetermined periodof time.

When generation of a normal termination trigger is confirmed at stepS51, control proceeds to step S52. At step S52, vehicle ECU 180 requestspower feeding device 200 through communication device 190 to stop powertransmission. Accordingly, voltage VH detected at voltage sensor 192 ofFIG. 4 begins to decrease. Waiting is conducted at step S53 untilvoltage VH become as low as a threshold value Vth (for example, 42V)sufficiently lower than the power supply voltage (for example, severalhundred V) of power storage device 150.

When VH<Vth is established at step S53, control proceeds to step S54. Atstep S54, welding check of system main relay SMR2 is executed. Thiswelding check can be made by disconnecting power storage device 150 fromvoltage sensor 192 with system main relay SMR2 at an OFF state, anddetecting voltage V2 through voltage sensor 192 at such a state.

If voltage V2 is not lower than the threshold voltage set sufficientlylower than the voltage of power storage device 150 at step S55, adetermination is made that power storage device 150 is not disconnectedand system main relay SMR2 is welded, whereby control proceeds to stepS59. At step S59, a determination result of welding occurred at systemmain relay SMR2 is ascertained, and stored/notified. At step S60, theprocess ends.

When voltage V2 is less than or equal to the threshold value setsufficiently lower than the voltage of power storage device 150 at stepS55, a determination is made that power storage device 150 isdisconnected, and system main relay SMR2 is not welded. In this case,control proceeds to step S56. At step S56, vehicle ECU 180 controlsrelay 112 to attain an OFF state such that secondary self-resonant coil110 does not resonate with primary self-resonant coil 240. At step S57,the process ends.

FIG. 9 is a flowchart representing a process in the case of forcedtermination due to an error occurring during power reception.

Referring to FIG. 9, whether an emergency stop trigger is generated ornot is monitored at step S101 during a power reception mode of thenon-contact power reception device of the vehicle. An emergency stoptrigger is generated when a failure that requires servicing of thevehicle has occurred such as damage at rectifier 130 or DC/DC converter140.

If such an emergency stop trigger is not generated, control proceeds tostep S106, and control is transferred to the main routine. In this case,the power reception condition is met, and secondary self-resonant coil110 is controlled to attain a state capable of power reception. Then,step S101 is executed at an elapse of a predetermined period of time.

When generation of an emergency stop trigger is confirmed at step S101,control proceeds to step S102. At step S102, vehicle ECU 180 requestspower feeding device 200 to stop power transmission throughcommunication device 190, and sets relay 112 at an OFF state so as toavoid power reception by resonating with secondary self-resonant coil110.

Accordingly, voltage VH detected at voltage sensor 192 of FIG. 4 beginsto decrease. Waiting is conducted at step S103 until voltage VH becomesas low as threshold value Vth (for example, 42V) sufficiently lower thanthe power supply voltage (for example, several hundred V) of powerstorage device 150.

When VH<Vth is established at step S103, control proceeds to step S104.At step S104, welding check of system main relay SMR2 is executed. Thewelding check is effected by disconnecting power storage device 150 fromvoltage sensor 191 with system main relay SMR2 at an OFF step, anddetecting voltage V2 through voltage sensor 191 in such a state.

When voltage V2 is not lower than the threshold value set sufficientlylower than the voltage of power storage device 150 at step S105, adetermination is made that power storage device 150 is not disconnected,and system main relay SMR is welded, whereby control proceeds to stepS107. At step S107, a determination result of welding occurring atsystem main relay SMR2 is ascertained, and stored/notified. Then, theprocess ends at step S108.

When voltage V2 is less than or equal to the threshold valuesufficiently lower than the voltage of power storage device 150, adetermination is made that power storage device 150 is disconnected andsystem main relay SMR2 is not welding at step S105. In this case,control proceeds to step S109 to achieve a charge stop state.

As described above, the non-contact power reception device of the firstembodiment takes a configuration in which the impedance is modified suchthat secondary self-resonant coil 110 does not resonate when powerreception is not desired at the vehicle. The modification is effected bymodifying the inductance by dividing the length of the coil with arelay. Accordingly, generation of an undesirable high voltage can beavoided since there is no portion for receiving the power electric powerat the vehicle even if power transmission is continued at the powerfeeding device side.

Second Embodiment

The second embodiment is a modification of the configuration ofsecondary self-resonant coil 110 shown in FIGS. 4 and 6 of the firstembodiment. Since the configuration of the remaining elements aresimilar to those of the first embodiment, description thereof will notbe repeated.

FIG. 10 is a circuit diagram of a configuration of secondaryself-resonant coil 110A employed in the non-contact power receptiondevice of the second embodiment.

Referring to FIG. 10, secondary self-resonant coil 110A is configured soas to be switchable between a first state and a second state. The firststate is selected in a power reception mode in which secondaryself-resonant coil 110A is magnetically coupled with primaryself-resonant coil 240 of FIG. 1 through resonance. The second state isselected in a power non-reception mode in which the coupling ofsecondary self-resonant coil 110A with primary self-resonant coil 240 isweaker than in the first state.

Secondary self-resonant coil 110A has an impedance differing between thefirst state and the second state. Specifically, secondary self-resonantcoil 110A includes a coil body 311, and a capacitance modifier 312Amodifying the capacitance of coil body 311.

Capacitance modifier 312A includes a leading line 321 connected to anend of the coil body, a relay 315 connected to leading line 321, and acapacitor 313 connected to coil body 311 via leading line 321 by relay315 in a power reception mode, and disconnected from coil body 311 byrelay 315 in a power non-reception mode.

Secondary self-resonant coil 110A further includes a dischargingresistor 314 for setting capacitor 313 at a discharging state in a powernon-reception mode. Discharging resistor 314 is connected across the twoelectrodes of capacitor 313. Capacitor 313 is connected between aleading line 322 connected to the other end of coil body 311 and relay315.

FIG. 11 is a circuit diagram representing a configuration of secondaryself-resonant coil 110A1 that is a modification of secondaryself-resonant coil 110A.

Referring FIGS. 10 and 11, secondary self-resonant coil 110A1 includes acapacitance modifier 312A1, instead of capacitance modifier 312A, in theconfiguration of secondary self-resonant coil 110A. Capacitance modifier312A1 is a version of capacitance modifier 312 of FIG. 10 havingdischarging resistor 314 deleted. The configuration of the remainingelements are similar to those of capacitance modifier 312, so that thedescription is not repeated.

FIG. 12 is a circuit diagram of a configuration of a secondaryself-resonant coil 110B that is a modification of secondaryself-resonant coil 110A.

Referring to FIGS. 10 and 12, secondary self-resonant coil 110B includesa capacitance modifier 312B, instead of capacitance modifier 312A, inthe configuration of secondary self-resonant coil 110A.

Capacitance modifier 312B includes a leading line 321 connected to anend of the coil body, a relay 315 connected to leading line 321, and acapacitor 313 connected with coil body 311 via leading line 321 by relay315 in a power reception mode, and disconnected from coil body 311 byrelay 315 in a power non-reception mode.

Secondary self-resonant coil 110B further includes a dischargingresistor 314 for setting capacitor 313 at a discharging state in a powernon-reception mode.

Secondary self-resonant coil 110B further includes another relay 316disconnecting discharging resistor 314 from capacitor 313 in a powerreception mode, and connecting the discharging resistor from thecapacitor in a power non-reception mode.

Discharging resistor 314 and another relay 316 are connected in seriesbetween the two electrodes of capacitor 313. Capacitor 313 is connectedbetween a leading line 322 connected to the other end of coil body 311and relay 315.

Vehicle ECU 180 of FIG. 4 controls relay 315 to attain an ON state andrelay 316 to attain an OFF state in a power reception mode, and controlsrelay 315 to attain an ON state and relay 316 to attain an OFF state ina power non-reception mode.

FIG. 13 is a circuit diagram of a configuration of a secondaryself-resonant coil 110C that is another modification of secondaryself-resonant coil 110A.

Referring to FIGS. 10 and 13, secondary self-resonant coil 110C includesa capacitance modifier 312C, instead of capacitance modifier 312A, inthe configuration of secondary self-resonant coil 110A.

Capacitance modifier 312C includes a leading line 321 connected to anend of the coil body, a relay 317 connected to leading line 321, and acapacitor 313 connected with coil body 311 via leading line 321 by relay317 in a power reception mode, and disconnected from coil body 311 bythe relay in a non-reception mode.

Secondary self-resonant coil 110C further includes a dischargingresistor 314 for setting capacitor 313 at a discharging state in a powernon-reception mode.

Relay 317 disconnects discharging resistor 314 from capacitor 313 in apower reception mode, and connects discharging resistor 314 withcapacitor 313 in a power non-reception mode.

Vehicle ECU 180 controls relay 317 such that an end of coil body 311 isconnected to one end of the capacitor, and discharging resistor 314 isdisconnected from that one end in a power reception mode. Vehicle ECU180 controls relay 317 such that an end of coil body 311 is disconnectedfrom one end of the capacitor, and that one end of the capacitor isconnected with discharging resistor 314 in a power non-reception mode.

As described above, even if power was transmitted from the power feedingdevice, the region where power reception by resonance is effected can beeliminated from the vehicle in the present embodiment when powerreception is not required.

Although each of the embodiments is described based on a series/paralleltype hybrid vehicle in which the driving power of engine 176 is split bypower split device 177 to be transmitted to driving wheel 178 and motorgenerator 172 as an electrical powered vehicle shown in FIG. 4, thepresent invention is also applicable to other types of hybrid vehicles.For example, the present invention is applicable to the so-called seriestype hybrid vehicle using engine 176 only for driving motor generator172, and the driving power of the vehicle is generated by motorgenerator 174 alone, a hybrid vehicle having only the regenerativeenergy among the kinetic energy generated by engine 176 collected aselectric energy, a motor assistant type hybrid vehicle using the engineas the main motive power and assisted by the motor as necessary, and thelike.

Further, the present invention is applicable to an electric vehicle thatruns only by electric power, lacking an engine 176, or a fuel cellvehicle further including a fuel battery in addition to power storagedevice 150 as the DC power source. Moreover, the present invention isalso applicable to an electrical powered vehicle 100 lacking a boostconverter 162.

It should be understood that the embodiments disclosed herein areillustrative and non-restrictive in every respect. The scope of thepresent invention is defined by the terms of the claims, rather than thedescription of the embodiments set forth above, and is intended toinclude any modifications within the scope and meaning equivalent to theterms of the claims.

The invention claimed is:
 1. A non-contact power reception devicecomprising: a load to which electric power is fed, and a receiving coilreceiving electric power to be supplied to said load from an externaltransmission coil, said receiving coil having a switching portionconfigured to switch between a first state and a second state, saidfirst state being selected in a power reception mode in which saidreceiving coil is magnetically coupled with said transmission coilthrough resonance of a magnetic field, and said second state beingselected in a power non-reception mode in which magnetic coupling ofsaid receiving coil with said transmission coil through resonance isweaker than in said first state, said receiving coil having an impedancediffering between said first state and said second state, said receivingcoil including a coil body, said coil body being divided at a centralregion into a first portion and a second portion, and said switchingportion including an inductance modifier modifying an inductance of saidcoil body, said inductance modifier including a relay provided at thecentral region of said coil body, connecting and disconnecting saidfirst portion and said second portion in a power reception mode and apower non-reception mode, respectively.
 2. A non-contact power receptiondevice comprising: a load to which electric power is fed, and areceiving coil receiving electric power to be supplied to said load froman external transmission coil, said receiving coil having a switchingportion configured to switch between a first state and a second state,said first state being selected in a power reception mode in which saidreceiving coil is magnetically coupled with said transmission coilthrough resonance of a magnetic field, and said second state beingselected in a power non-reception mode in which magnetic coupling ofsaid receiving coil with said transmission coil through resonance isweaker than in said first state, said receiving coil including a coilbody, and said switching portion including a capacitance modifiermodifying a capacitance of said coil body, said capacitance modifierincluding a leading line connected to an end of said coil body, a relayconnected to said leading line, and a capacitor connected to said coilbody via said leading line by said relay in a power reception mode, anddisconnected from said coil body by said relay in a power non-receptionmode.
 3. The non-contact power reception device according to claim 2,further comprising a discharging resistor for setting said capacitor ata discharging state in a power non-reception mode.
 4. The non-contactpower reception device according to claim 3, further comprising anotherrelay disconnecting said discharging resistor from said capacitor in apower reception mode, and connecting said discharging resistor with saidcapacitor in a power non-reception mode.
 5. The non-contact powerreception device according to claim 3, wherein said relay disconnectssaid discharging resistor from said capacitor in a power reception mode,and connects said discharging resistor with said capacitor in a powernon-reception mode.
 6. The non-contact power reception device accordingto claim 1, further comprising: a voltage converter voltage-convertingan input voltage for supply to said load, and a rectifier rectifying ACvoltage and providing the rectified voltage to said voltage converter assaid input voltage, wherein said receiving coil receives electric powerfrom said transmission coil, and generates said AC voltage to besupplied to said rectifier.
 7. The non-contact power reception deviceaccording to claim 1, wherein said non-contact power reception device ismounted on a vehicle, and receives electric power from said externaltransmission coil, said non-contact power reception device furthercomprising a control unit performing control to switch said receivingcoil between said first state and said second state, wherein saidcontrol unit sets said receiving coil at said first state and at saidsecond state when said vehicle meets and not meets a power receptioncondition, respectively.
 8. The non-contact power reception deviceaccording to claim 7, wherein said vehicle includes a power storagedevice receiving charge electric power from said non-contact powerreception device as said load, said power reception condition includesthe condition that a state of charge of said power storage device isless than a threshold value.
 9. The non-contact power reception deviceaccording to claim 7, wherein said power reception condition includesthe condition that a predetermined failure is not occurring at saidvehicle.
 10. A vehicle comprising the non-contact power reception deviceaccording to claim
 1. 11. The non-contact power reception deviceaccording to claim 2, further comprising: a voltage convertervoltage-converting an input voltage for supply to said load, and arectifier rectifying AC voltage and providing the rectified voltage tosaid voltage converter as said input voltage, wherein said receivingcoil receives electric power from said transmission coil, and generatessaid AC voltage to be supplied to said rectifier.
 12. The non-contactpower reception device according to claim 2, wherein said non-contactpower reception device is mounted on a vehicle, and receives electricpower from said external transmission coil, said non-contact powerreception device further comprising a control unit performing control toswitch said receiving coil between said first state and said secondstate, wherein said control unit sets said receiving coil at said firststate and at said second state when said vehicle meets and not meets apower reception condition, respectively.
 13. The non-contact powerreception device according to claim 12, wherein said vehicle includes apower storage device receiving charge electric power from saidnon-contact power reception device as said load, said power receptioncondition includes the condition that a state of charge of said powerstorage device is less than a threshold value.
 14. The non-contact powerreception device according to claim 12, wherein said power receptioncondition includes the condition that a predetermined failure is notoccurring at said vehicle.
 15. A vehicle comprising the non-contactpower reception device according to claim 2.